Bildtext:Jack Dorsey, chairman and co-founder of Twitter Inc., center, speaks as New York City Mayor Michael 'Mike' Bloomberg, right, and San Francisco Mayor Edward 'Ed' Lee listen during a press conference in San Francisco, California, U.S., on Friday, June 14, 2013. Dorsey, Mayor Bloomberg and Mayor Lee announced today that they will co-host the second annual Bloomberg Technology Summit to be held in New York on September 30. Photographer: David Paul Morris/Bloomberg via Getty Images

Bildtext:

Jack Dorsey, chairman and co-founder of Twitter Inc., center, speaks as New York City Mayor Michael 'Mike' Bloomberg, right, and San Francisco Mayor Edward 'Ed' Lee listen during a press conference in San Francisco, California, U.S., on Friday, June 14, 2013. Dorsey, Mayor Bloomberg and Mayor Lee announced today that they will co-host the second annual Bloomberg Technology Summit to be held in New York on September 30. Photographer: David Paul Morris/Bloomberg via Getty Images

Jack Dorsey chairman and cofounder of Twitter Inc center speaks as... NyhetsfotoAmerika,Ed Lee,Finansväsen,Grundare,Horisontell,Internet,Jack Dorsey,Kalifornien,Lyssna,Michael Bloomberg,Möte,Nordamerika,Ordförande,Politik,Prata,Presskonferens,Regering,San Francisco - Kalifornien,Snabbmeddelanden,Socialt nätverkande,Staden New York,Teknologi,Toppmöte,Twitter,USAPhotographer BloombergCollection: Bloomberg 2013 BloombergJack Dorsey, chairman and co-founder of Twitter Inc., center, speaks as New York City Mayor Michael 'Mike' Bloomberg, right, and San Francisco Mayor Edward 'Ed' Lee listen during a press conference in San Francisco, California, U.S., on Friday, June 14, 2013. Dorsey, Mayor Bloomberg and Mayor Lee announced today that they will co-host the second annual Bloomberg Technology Summit to be held in New York on September 30. Photographer: David Paul Morris/Bloomberg via Getty Images